Uric acid levels and the risk of Contrast Induced Nephropathy inpatients undergoing coronary angiography or PCI

Background and aim: Contrast Induced Nephropathy (CIN) is a common complication of procedures that require the use of contrast media, and seems to be mediated by oxidative stress and reactive oxygen species generation. Hyperuricemia is characterized by inhibited nitric oxide system and enhanced synthesis of reactive oxygen species. However, few studies have so far investigated the association between hyperuricemia and CIN that is therefore the aim of the current study among patients undergoing coronary angiography or percutaneous intervention. Methods and results: We analyzed a total of 1950 patients with Creatinine clearance <90ml/min) undergoing elective or urgent coronary angiography and/or angioplasty. Patients weredividedaccording to tertiles of baseline uric acid (Group 1, ≤5.5mg/dL n=653; Group2, 5.6-7.0mg/dL, n=654; Group 3, ≥7.0mg/dL, n=643). CIN was defined as an absolute ≥0.5mg/dl or a relative ≥25% increase in the serum creatinine level at 24 or 48h after the procedure. Patients with higher uric acid levels were older, previous smokers, with higher prevalence of hypertension and diabetes, but with lower family history of CAD. They had more often history of a previous CABG and baseline renal dysfunction. Patients of the third Tertile had also higher levels of white blood cells, higher triglycerides and lower HDL-cholesterol and higher percentage of dilated cardiomyopathy/valvular disease as indication for angiography and consequently a lower prevalence of PCI. Patients with higher SUA were more often on therapy with ACE inhibitors and diuretics, but less often with statins, nitrate, ASA and Clopidogrel at admission. The occurrence of CIN was observed in 251 patients (12.9%), and was significantly associated with uric acid levels (12.3% in Group 1, 10.4% in Group 2 and 16.0% in Group 3; p=0.04). Similar results were observed when the analysis was performed according to each tertiles values in both male and female gender. The association between elevated uric acid(≥7mg/dl) and CIN was confirmed by multivariate analysis after correction for baseline confounding (Adjusted OR [95%CI]=1.42 [1.04-1.93], p=0.026). Similar results were observed across major subgroups of high-risk patients, such as patients with diabetes, female gender, renal failure, hypertension, and elderly. Conclusions: This is the first large study showing that among patients undergoing coronary angiography or percutaneous interventions elevated uric acid level is independently associated with an increased risk of CIN.